Messages in this thread | | | Subject | Re: [PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount | From | Nayna <> | Date | Mon, 7 Aug 2017 19:55:49 +0530 |
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On 08/07/2017 05:22 PM, Peter Huewe wrote: > > > Am 7. August 2017 13:46:32 MESZ schrieb Nayna Jain <nayna@linux.vnet.ibm.com>: >> The TPM burstcount status indicates the number of bytes that can >> be sent to the TPM without causing bus wait states. Effectively, >> it is the number of empty bytes in the command FIFO. Further, >> some TPMs have a static burstcount, when the value remains zero >> until the entire FIFO is empty. >> >> This patch ignores burstcount, permitting wait states, and thus >> writes the command as fast as the TPM can accept the bytes. >> The performance of a 34 byte extend on a TPM 1.2 improved from >> 52 msec to 11 msec. >> >> Suggested-by: Ken Goldman <kgold@linux.vnet.ibm.com> in >> conjunction with the TPM Device Driver work group. >> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com> >> Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > > Are you sure this is a good idea? > On lpc systems this more or less stalls the bus, including keyboard/mouse (if connected via superio lpc).
Thanks Peter for quick response.
I actually meant to post this patch as RFC. Sorry, missed that. It was meant to be a starting place for the discussion related to burst_count.
> > On which systems have you tested this? > Spi/Lpc? Architecture?
Tested it with LPC on x86.
> > This might not be noticable for small transfers, but think about much larger transfers....
I did the following testing:
* Ran a script with 1000 extends. This was to test continuous extends which are generally in large numbers when IMA is enabled.
* Ran a command to ask TPM to hash big size file like 1MB. This was to test the long command.
In both of the above cases, I didn't face any tpm specific errors.
Is there any test-script or test-cases which I can try to test the scenario(stalling the bus, including keyboard/mouse) with the patch ?
Thanks & Regards, - Nayna
> > Imho: NACK from my side. > > Thanks, > Peter > >> --- >> drivers/char/tpm/tpm_tis_core.c | 45 >> ++--------------------------------------- >> 1 file changed, 2 insertions(+), 43 deletions(-) >> >> diff --git a/drivers/char/tpm/tpm_tis_core.c >> b/drivers/char/tpm/tpm_tis_core.c >> index b617b2eeb080..478cbc0f61c3 100644 >> --- a/drivers/char/tpm/tpm_tis_core.c >> +++ b/drivers/char/tpm/tpm_tis_core.c >> @@ -255,9 +255,7 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 >> *buf, size_t count) >> static int tpm_tis_send_data(struct tpm_chip *chip, u8 *buf, size_t >> len) >> { >> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev); >> - int rc, status, burstcnt; >> - size_t count = 0; >> - bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND; >> + int rc, status; >> >> status = tpm_tis_status(chip); >> if ((status & TPM_STS_COMMAND_READY) == 0) { >> @@ -270,49 +268,10 @@ static int tpm_tis_send_data(struct tpm_chip >> *chip, u8 *buf, size_t len) >> } >> } >> >> - while (count < len - 1) { >> - burstcnt = get_burstcount(chip); >> - if (burstcnt < 0) { >> - dev_err(&chip->dev, "Unable to read burstcount\n"); >> - rc = burstcnt; >> - goto out_err; >> - } >> - burstcnt = min_t(int, burstcnt, len - count - 1); >> - rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality), >> - burstcnt, buf + count); >> - if (rc < 0) >> - goto out_err; >> - >> - count += burstcnt; >> - >> - if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c, >> - &priv->int_queue, false) < 0) { >> - rc = -ETIME; >> - goto out_err; >> - } >> - status = tpm_tis_status(chip); >> - if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) { >> - rc = -EIO; >> - goto out_err; >> - } >> - } >> - >> - /* write last byte */ >> - rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[count]); >> + rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality), len, >> buf); >> if (rc < 0) >> goto out_err; >> >> - if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c, >> - &priv->int_queue, false) < 0) { >> - rc = -ETIME; >> - goto out_err; >> - } >> - status = tpm_tis_status(chip); >> - if (!itpm && (status & TPM_STS_DATA_EXPECT) != 0) { >> - rc = -EIO; >> - goto out_err; >> - } >> - >> return 0; >> >> out_err: >
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